I have just finished reading Valter Longo’s The Longevity Diet, and while I was expecting more elaboration on his Fasting Mimicking Diet, Dr. Longo presented something entirely new: a longevity-focused variant of the Mediterranean Diet. Where appropriate, he does drop in a few references to the Fasting Mimicking Diet throughout the book, but he is careful to point out that it should be done under professional supervision.

Dr. Longo does look at commonalities amongst communities with a high frequency of centenarians, but he is influenced by the cuisine of his hometown in Italy. At the same time, he is careful not to stray too far from the standard nutrition orthodoxy, specifically with respect to saturated fats (more on that later).

One diet does not fit all

What I found most valuable were the age-targeted optimal diets. Dr. Longo makes a good point that the optimal diets we should focus on during middle age will differ than the ones we should adopt in our senior years. The objective in the early years would be to optimize the body’s repair mechanisms and minimizing overuse of metabolic pathways that accelerate the aging process. These optimizations become less important later in life when the priority becomes the maintenance of muscle mass.

Dr. Longo further elaborates that age differences are not the only criteria for the optimal diet, and he writes that “the levels of some dietary components must be modified depending on a person’s age, physical state and based on his or her genes.” This is something I have long believed and written about in many articles and comments on this website.

Low animal protein intake increases longevity

One age-specific recommendation was with respect to protein intake. The book stresses that low-protein intake extends longevity because it is associated with the reduction in cancer rates. This is especially important in people for whom maintenance of weight and muscle is not a problem, which typically means those aged sixty-five and younger. Those above sixty-six or those with the genetic predisposition to being thin must increase their protein intake to maintain a healthy weight and muscle strength.

As discussed elsewhere on this site, we know that the Insulin-Like Growth Factor 1 hormone (IGF-1) is triggered by protein intake. This hormone is essential for growth in children and teenagers, and it triggers an anabolic pathway for muscle building processes. However, what Dr. Longo alludes to are a number of studies that have shown this hormone’s culpability in accelerating the aging process.

What Calorie Restriction Diets do is keep levels of this hormone less elevated over time. Dr. Longo goes further by suggesting that strict low-protein diets are less optimal later in life. In our senior years, we produce less IGF-1, and maintenance of muscle mass becomes a bigger problem. We become prone to physical injury because our muscles are unable to support the functional movement that we take for granted in the earlier years. Lower levels of IGF-1 in elderly people are associated with frailty, immune system dysfunction, and difficulty with wound healing.

Dr. Longo writes that “this problem does not require complex changes and is solved by maintaining the Longevity Diet until age sixty-five or seventy, then gradually increasing one’s level of protein and general nourishment by 10 to 20 percent to maintain a healthy weight and muscle strength.”

Ketogenic diets are low in protein intake

It is a common mistake to presume that ketogenic diets are high in animal proteins. This is absolutely not the case. In fact, protein kicks you out of ketosis because your body prioritizes protein metabolism through a process called gluconeogenesis before switching to fat as the primary fuel.

Dr. Longo makes this mistake on several occasions throughout his book when taking a negative view on high-fat low-carbohydrate diets by associating it with the increased risk of cancer. He makes several erroneous assumptions to conclude that ketogenic diets are not conducive to longevity:

– He confuses the Ketogenic Diet with the Atkins Diet because the mechanism by which the Atkins Diet works is the switch to burning protein and fat as the primary fuel. It is far easier to metabolize fat in a Ketogenic Diet that maintains lower levels of protein intake.Dr. Valter Longo’s Longevity Diet is best understood in the context of what makes the Mediterranean Diet so successful at increasing lifespan and healthspan in humans.

– He assumes that the protein is sourced primarily from animal sources, but this is neither true nor is it recommended to have a high protein intake to achieve nutritional ketosis.

– He conveniently misses the results of his own cancer research with respect to the protective mechanisms triggered by fasting. In his own words, he attributes the success to lower levels of IGF-1, lower levels of glucose, higher levels of ketone bodies, and higher levels of a growth factor inhibitor (IGFBP1). These are all effects of entering nutritional ketosis, which can be achieved just as efficiently with intermittent fasting or a ketogenic diet.

– The book is not updated with the latest research on ketogenic diet effects on longevity and healthspan in adult mice, published in September 2017.

The main take on this commentary is that “one diet does not fit all.” It is true that a ketogenic diet is not for everyone, and there are many variations of intermittent fasting, including ones that are completely and thoroughly vegan. Vegan Intermittent Fasting is one of my favorite areas of research, especially as vegan diets emphasize foods that are high in polyphenol content, which are also associated with longevity.

The Link to the Mediterranean Diet

My view on the Longevity Diet is that it is very much a variation of the Mediterranean Diet. Dr. Longo’s recommendation is to eat mostly vegan with time-restricted feeding. Proteins should be minimized and sourced from plants. To manage deficiencies in vegan diets, he adds seafood two or three times per week. Seafood sourced protein should be low in mercury: salmon, trout, cod, sea bream, sardines, anchovies, shrimp, and clams.

The Longevity Diet shares the following characteristics with the Mediterranean Diet:

– high intake of olive oil,

– lots of legumes,

– unrefined cereals,

– lower intake of cheese sourced from cow milk (goat and sheep dairy is more common),

– moderate wine consumption,

– low meat consumption,

– low milk consumption,

– low egg consumption,

– low butter consumption,

– lots of vegetables,

– nuts (almonds, walnuts, and hazelnuts)

The Longevity Diet emphasizes a few more restrictions to promote longevity:

– It is more specific about protein intake (0.36 grams of protein per pound of body weight).

– It prescribes age-specific variations to food consumption.

– It introduces time-restricted feeding.

The Fasting Mimicking Diet

The book only briefly describes the Fasting Mimicking Diet. Dr. Longo is careful not to recommend a self-administered fasting regimen because of complications that can arise for people on medication and others with health issues and genetic intolerance to a particular nutrient composition. He directs his readers the ProLon meal plan with advice to seek assistance from qualified professionals that understand how the diet is administered.

Dr. Longo recommends the fasting regimen once a month for overweight patients with metabolic syndrome. The frequency is reduced for healthier patients. The regimen starts with a week of preparation by following the Longevity Diet described above with omega-3 supplements taken on twice during the week.

On day 1, intake is reduced to 1,100 calories, with 500 calories sourced from vegetables (broccoli, tomatoes, carrots, etc.) and 500 from nuts and olive oil. The diet prescribes infrequent vitamin supplementation (1 multivitamin, 1 mineral supplement, and 1 omega-3/omega-6 supplement). The diet includes 3 to 4 cups of tea per day without sugar. The only protein intake is 25 grams sourced from nuts. Water is unlimited.

On days 2 to 5, the calories go down to 800, with half coming from complex vegetables and half coming from nuts and olive oil. Vitamin supplementation remains the same (1 multivitamin, 1 mineral supplement, and 1 omega-3/omega-6 supplement). The diet continues with 3 to 4 cups of tea per day without sugar and unlimited water.

On day 6, the transition diet begins. This is basically the Longevity Diet described above but without the fish or any animal-sourced proteins.

The time-restricted feeding is observed at all times, with the window for eating being 11-12 hours and typically divided into two meals and a snack.

Effects of the Fasting Mimicking Diet

Weakness, hunger, and headaches that are typical of fasting regimens do not go away. They are listed by Dr. Longo as side effects that are usually reduced by day 4 or 5 and eliminated entirely by the second or third monthly fasting cycle.

On the positive side, people experience the same benefits attributed to intermittent fasting: glowing and younger-looking skin, stronger mental focus, ability to resist binging after resuming a normal diet, decreased appetite for sugar, and decreased dependence on alcohol, caffeine, and other addictive substances.


Longo, Valter. 2018. The Longevity Diet [Kindle version].

Roberts, MN et al. “A Ketogenic Diet Extends Longevity and Healthspan in Adult Mice.” Cell Metab 26.3 (2017):539-546.